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Dynamax 8 SCT Restore

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#1 RDFox

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Posted 26 August 2020 - 10:54 PM

Thanks to woodsman (Rich), I have acquired an early Criterion Dynamax 8 SCT. I know the quality history these scopes have. This seems to an early model, this could be good, or bad. Since my Cave Astrola 12.5” restoration is done it’s time to dive into something new. I’ll keep all progress posted here. 

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#2 RDFox

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Posted 26 August 2020 - 10:58 PM

Question; does anyone know what’s under this emblem? I’m thinking that there is some kind of shaft bearing or keeper under it. Some advice would be great, before I try to grind the rivets and remove it.

 

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#3 apfever

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Posted 27 August 2020 - 02:33 AM

Go to around the 8th page of this string.

 

Dynamax mount link

 

I have a ton of pictures I never got back to on the complete restoration. I did some minor improvements. I did some self challenge on this mount.  I added 4 more clutch disc bolts, but with tighter clearances than original and accurate so that the plates could be rotated to any position and still have all the bolts work (symmetry of layout). 

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#4 apfever

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Posted 27 August 2020 - 02:43 AM

I found the files, files of files of pictures.  I completely reset the wild main bearing, found the intricate way to re grease it, must be 30 or 40 pictures of the complete build. I won't be able to remember it all now, but I have the pictures. I can send a file in email I think...data limit maybe.  

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#5 apfever

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Posted 27 August 2020 - 02:54 AM

I do remember this part.  What started the rebuild was the manual RA knob assembly.  The hole in the blue plate is slightly enlarged to allow setting the gear mesh. The original lock washer is the split ring on the right.

The split in the lock washer had popped into the enlarged hole in the plate. This kinked the knob assembly and also tossed the gear mesh out. I replace the split ring lock washer with the external star type. I probably also reset clearances and other washers in the assembly - not sure.

 

That's all for here. I can't afford to get lost trying to remember it all.

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#6 RDFox

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Posted 27 August 2020 - 10:52 AM

Thanks, this info really helps. I’ll go to that link and look. RD



#7 RDFox

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Posted 29 August 2020 - 11:39 AM

I did figure out how to lubricate the main bearing on the shaft. There is a small in the side. Since I have greased many a car and cycle, this needs a small needle grease tip. Basically you can use a medical syringe filled with grease. Easier than most mount bearings.

DynascopebearingA.jpg
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#8 Gil V

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Posted 29 August 2020 - 01:07 PM

You can usually pull the rivets out with pliers. Twisting motion can help.

It covers the upper RA thrust bearing, which has a screw and fender washer helping to keep it secure.

Edited by Gil V, 29 August 2020 - 01:36 PM.


#9 Gil V

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Posted 29 August 2020 - 01:09 PM

You don’t want to pop the RA base off the RA gear assembly unless absolutely necessary. You need an arbor press to re-assemble it.
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#10 RDFox

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Posted 29 August 2020 - 04:46 PM

I have a press, it came off rather easily. I’m extremely lucky!!!!!



#11 apfever

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Posted 29 August 2020 - 07:23 PM

That fancy bearing has a double shell inside. The grease needle can go further in by rotating the bearing till dual holes align. It's a little funky and takes a little feel. Use a thin rod (or the needle) and tap it in the outside hole, move the needle in and out as you rotate to different positions. Wiggle the needle around, tap around inside when you are checking a position. You should find a position where the needle will go further into the bearing. 

 

Since you have the bearing off the shaft:

It is important you place it back on the shaft correctly.  There is a recess in the shaft where the holding set screw bottom into.  You need to loosely bottom the set screw into the recess in the shaft. Then move the bearing down as far as possible so the set screw is nested into the bottom edge of the recess. Hold the bearing in that position and finish tightening the set screw. It is important that the set screw is anchored into the bottom EDGE of the shaft recess, and NOT just tightened against the side of the shaft. This keeps the bearing from moving down the shaft when the the assembly is pressed back into the base.



#12 clamchip

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Posted 29 August 2020 - 07:36 PM

Make sure the grease you use is 'compatible with all greases' since you are

not cleaning out all the old stuff.

Most chassis lubes are compatible since you can't very well clean out ball joints

etc.

 

Robert


Edited by clamchip, 29 August 2020 - 07:41 PM.


#13 apfever

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Posted 29 August 2020 - 07:38 PM

I tried a picture. This is the best I can get straight lines while free form with the computer mouse.  Hmmm, maybe I can slide the mouse on a straight edge.  I have some permanent nerve damage from elbows to index finger tips on each fore arm. Some days are worse than others. The ol' fore arm sensation can really light up during anxiety or strong emotions like a public speech (most common anxiety), even strong anticipation of seeing a new old scope, anything triggering adrenaline.  This Dynamax assembly doesn't do a thing to me, it's just been a hectic day.

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#14 Stevegeo

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Posted 29 August 2020 - 07:53 PM

Question, what's the serial number of yours?

 

Mine was painted black after the previous owners restoration.  The focuser is probably the smoothest of any scope I have ever felt after regreasing .    

The drive is dead quiet, and dead on tracking.. for what I have into mine, it's a keeper.

 

Stevegeo 



#15 apfever

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Posted 29 August 2020 - 07:54 PM

Make sure the grease you use is 'compatible with all greases' since you are

not cleaning out all the old stuff.

 

Robert

I used Super Lube as in my pictures of this proceedure, Post #4 above.   My bearing then went through a number of rotations, including rotations under pressure on a drill press to simulate actual use. I'm also guessing that it sat around for at least a month or so while I worked with it, giving the mix of greases a little time to react.  I never notices any signs of foul witches brew. YMMV. .

 

These pictures are several years old. Both of my Dynascopes were sold years ago now.  I have more pics.

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#16 apfever

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Posted 29 August 2020 - 07:57 PM

Last entry on this aspect. Hope it helps.  The green arrow is the grease hole, the red arrow is the set screw hole.

Testing under pressure.

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Edited by apfever, 29 August 2020 - 07:59 PM.

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#17 RDFox

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Posted 29 August 2020 - 09:18 PM

OMG! Thank you to everyone one this thread! You’re amazing. Such great advice and probably saving the scope, because I’m sure I would break something on my own. You can not know how much I appreciate this! One thing I am learning, scopes are as about as unique as people. No two are the same. They all have their quirks.


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#18 Gil V

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Posted 30 August 2020 - 09:02 AM

Another thing - generally, it’s easier to work with the drive base if you take the fork arms off.

#19 RDFox

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Posted 30 August 2020 - 10:50 AM

Another thing - generally, it’s easier to work with the drive base if you take the fork arms off.

What?

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#20 Gil V

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Posted 30 August 2020 - 12:20 PM

Once you are ready to reassemble, reach out to me. There are several things I want you to check before you press the thrust bearing back on.

#21 RDFox

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Posted 30 August 2020 - 02:21 PM

Will do, thanks



#22 RDFox

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Posted 30 August 2020 - 10:22 PM

Question, what's the serial number of yours?

 

Mine was painted black after the previous owners restoration.  The focuser is probably the smoothest of any scope I have ever felt after regreasing .    

The drive is dead quiet, and dead on tracking.. for what I have into mine, it's a keeper.

 

Stevegeo 

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#23 Stevegeo

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Posted 31 August 2020 - 03:30 AM

That is a low number....  

Mine is 4372.... 

Stevegeo. 



#24 RDFox

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Posted 01 September 2020 - 06:40 AM

I tried a picture. This is the best I can get straight lines while free form with the computer mouse.  Hmmm, maybe I can slide the mouse on a straight edge.  I have some permanent nerve damage from elbows to index finger tips on each fore arm. Some days are worse than others. The ol' fore arm sensation can really light up during anxiety or strong emotions like a public speech (most common anxiety), even strong anticipation of seeing a new old scope, anything triggering adrenaline.  This Dynamax assembly doesn't do a thing to me, it's just been a hectic day.

shaft.jpg



#25 Maximumron

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Posted 09 September 2020 - 01:45 PM

Hey everyone. I'm in the midst of trying to figure out if my DX-8 has issues with the focusing mechanism. Did you or, has anyone has experience with how its assembled and its function?

I collimated the scope a few weeks ago on Izar in Bootes. I think it came out pretty good as I could distinguish color and, at times of good seeing, just barely split the two. When I hooked my DSLR to it, focusing was a different story. I was setup at prime focus and either ran our of room or, the mechanism bound up a little. Been thinking of pulled the system apart but...that seems like a lot of risky work.

Any body have any thoughts??? Id be most appreciative. :-)




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